Nearly 50 percent of oral carcinomas contain p53 mutations, making mutant p53 peptides attractive candidates for use in cancer vaccines. The probability is greater, however, that tumors will present wild-type sequence (wt) peptides derived from mutant p53 rather than mutant peptides. Our research is guided by the hypothesis that the effectiveness of vaccines targeting wt p53 epitopes will be influenced by (1) the ability of a patient's tumor to present wt p53 epitopes for immune recognition and (2) the ability of the patient's T-cells to respond to these epitopes. Our ongoing analysis of these factors, which focuses on the first of four CTL-defined wt p53 epitopes identified, p53, indicates that: 1) nature or site of an alteration in p53 influences processing and presentation of this epitope and, perhaps, other epitopes as well; 2) only a third of PBMC of either normal donors or patients responded ex vivo to this epitope; and 3) tumors of "responsive" patients had little/no potential to present wt p53 epitopes, suggesting that the outgrowth of "epitope-loss" tumors might have occurred in these patients. At the same time, a consensus is developing that multiple epitope-based vaccines may be required for tumor rejection. The identification of five T-cell defined wt p53 epitopes for vaccine use, including a DR4-restricted, Th-dedined wt p53 epitope that we recently identified, raises issues about how best to construct p53-based vaccines. The specific aims of this project focus on these issues and are aimed at determining ex vivo: 1) the responsiveness of HLA-A2+ and/or HLA-DR4+ patients to the identified class I and class II HLA-restricted wt p53 epitopes, 2) ability of patient?s tumors to present these epitopes based on a comparative analysis of p53 expressed in established cell lines with p53 expressed in patients' tumors, and 3) evaluate the efficacy of DC-based vaccines employing various combinations and sources of wt p53 epitopes in the induction of T cells recognizing CTL.